The present invention relates to a method of forming a carbon doped oxide layer on a substrate, when making a semiconductor device.
Semiconductor devices include metal layers that are insulated from each other by dielectric layers. As device features shrink, reducing the distance between the metal layers and between metal lines on each layer, capacitance increases. To address this problem, insulating materials that have a relatively low dielectric constant are being used in place of silicon dioxide to form the dielectric layer that separates the metal lines.
A material that may be used to form such a low k dielectric layer is carbon doped oxide (xe2x80x9cCDOxe2x80x9d). Using this material instead of silicon dioxide to separate metal lines may yield a device having reduced propagation delay, cross-talk noise and power dissipation. A CDO layer may be deposited on a substrate using a plasma enhanced chemical vapor deposition (xe2x80x9cPECVDxe2x80x9d) process. When using such a process to form such a layer, gases that provide a source of silicon, oxygen, and carbon must be fed into a PECVD reactor. Examples of such gases include those having the formula (CH3)xSi(OCH3)4xe2x88x92x, e.g., tetramethoxysilane, methyltrimethoxysilane, dimethyldimethoxysilane, and trimethylmethoxysilane. A background gas, e.g., an inert gas such as helium, may be fed into the reactor at the same time. That reactor may then be operated at conventional pressures, temperatures, RF and power for a time sufficient to deposit a CDO layer of the desired thickness onto the substrate.
Although processes that use (CH3)xSi(OCH3)4xe2x88x92x precursors to form CDO layers may produce layers that have a dielectric constant that is less than 3.0, those processes generate those layers at a relatively low deposition rate. Accordingly, there is a need for an improved process for making a CDO insulating layer. There is a need for such a process that generates a CDO layer from a (CH3)xSi(OCH3)4xe2x88x92x precursor at an increased deposition rate. The method of the present invention provides such a process.